Rule broken by English knight in branch of church (12)
I believe the answer is:
denomination
'church' is the definition.
(thesaurus)
'rule broken by english knight in branch' is the wordplay.
I cannot really see how this works, but
'by' could be 'at' and 'at' is found within the answer.
'english' could be 'e' (abbreviation as in OED) and 'e' is found in the answer.
'knight' could be 'n' (chess abbreviation) and 'n' is found in the answer.
'rule' could be 'dominion' (synonyms) and 'dominion' is found in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for denomination that I've seen before include "Face value of a banknote, coin or postage stamp" , "sect" , "Religious group - grade in series of designated values" , "Note's face value" , "Value of postage stamp; branch of religion" .)